准噶尔盆地西北缘克-百断裂带石炭系油气成藏控制因素新认识

针对准噶尔盆地西北缘克-百断裂带上盘石炭系老油区勘探的有利储层分布规律、成藏模式和油气藏类型等关键技术难题展开研究,对其控制因素进行了重建。克-百断裂带上盘石炭系的有利储层受断裂、裂缝和长时间风化淋滤控制,储层渗流能力主要决定于微裂缝,而微裂缝主要分布于断裂附近2～3km范围内,断裂间距2～5km,提出了有利储层不受岩性控制、整带分布、沿断裂更发育等新认识,改变了有利储层受安山岩控制、局部分布的原认识。通过重建成藏模式和油藏类型,提出油气沿断裂带富集,改变了断裂起封堵作用的原认识;油藏类型由断块—岩性油藏变为断裂富集的大型地层油藏,由局部含油变为整带含油。在新认识指导下重新勘探,扩大了勘探范围,2005—2007年新增石油探明储量超过以往50年探明石油地质储量之和。

Discussion on controlling factors for Carboniferous hydrocarbon accumulation in the Ke-Bai fractured zone of the northwestern margin in Junggar Basin

The upper-plate Carboniferous of the Ke-Bai fractured zone were studied for revealing some key problems about the distribution of the favorable reservoirs, pool-forming pattern and reservoir types. The favorable reservoirs were controlled by faults, fractures and long-time weathered and leached regions. The permeability of reservoirs was controlled by the enrichment degree of micro fractures, which mainly distributed in the region from two to three kilometers near the faults with the spaces of 2-5 kilometers. So, the lithological aspect did not affect the distribution of favorable reservoirs. The favorable reservoirs covered the whole fault belt and best developed in the faults. The rebuilt pool-forming patterns and reservoir types showed the regularity of oil and gas abounded along the fault belts and changed the understanding about the reservoir type from fault-lithologic type to large lithostratigraphic type. The whole fault belt was considered as oil-bearing region. The new understanding improved the increase of exploration range in this area. In recent three years, the proved reserves of Ke-Bai fractured zone are more than the total reserves in the past 50 years.